The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses.
In certain power supply systems, such as UPS systems, there is no direct measurement available to determine the status of rectifier fuses, whether blown or normal. In order to ensure safe, reliable and proper operation, the status of the rectifier fuses must be determined correctly and efficiently. FIG. 1 is a simplified schematic of such a prior art UPS system 100.
UPS system 100 includes an AC/DC converter 102, a DC/AC converter 104, and a DC back-up power source 106. UPS system 100 provides uninterruptible power at a load voltage (such as 480 VAC) to a load. The load may illustratively be equipment in a facility or part of a facility, such as computer systems in a data room. UPS system 100 may further include a bypass switch (not shown) which may be used to couple input power to UPS system 100 to the load bypassing the AC/DC converter 102 and the DC/AC converter 104.
UPS system 100 may illustratively be a three-phase UPS system. The input AC power is three phase AC with three legs V_ac-in_A, V_ac-in_B, V-ac-in-C of the power feed, such as from a power feed from a utility company, coupled through three poles of circuit breaker 112 to filter inductors Lin1-3 and input fuses F1-3 to an input 120 of AC/DC converter 102. Fuses F1-3 may be referred to herein as “rectifier fuses” as AC/DC converter 102 is typically a rectifier, such as described below. Illustratively, the three phase input AC power is 480 VAC.
AC/DC converter 102 converts the AC power to DC that is provided to a DC bus 118 at an output 122 of AC/DC converter 102. An input 124 of a DC/AC converter 104 is coupled to DC bus 118. DC/AC converter 104 converts the DC on DC bus 118 to AC at an output 126 of UPS system 100. Back-up DC power source 106 is also coupled to DC bus 118. A filter inductor LDC may illustratively couple a negative side of output 122 of AC/DC converter 102 to a negative side of DC bus 118.
UPS system 100 includes a control module 132 that controls UPS system 100. Control module 132 has inputs 134 and outputs 136 coupled to various elements of UPS system 100, as described in more detail below. Control module 132 may illustratively be a computer, a microcontroller, a digital signal processor, or other programmable device that is programmed with software to control UPS system 100.
UPS system 100 illustratively has the following measurements available: two current transformers CT1 and CT2 at the output side of circuit breaker 112 on two of the three legs of the three phase AC input power, three phase input voltage measurements, such as at the poles of circuit breaker 112. Optionally, there may be a third current transformer CT3 as shown in phantom FIG. 1 In this regard, the current transformers and other sensors are coupled to respective inputs 134 of control module 132. But UPS system 100 does not have any existing measurements of the voltage differences across the fuses F1, F2 and F3 from which the status of these fuses can be directly determined.
AC/DC converter 102 and DC/AC converter 104 illustratively include switched semiconductor devices as described in more detail below. These devices have gate inputs coupled to respective outputs 136 of control module 132. Control module 132 gates the switched devices of AC/DC converter 102 and DC/AC converter 104 in known fashion to control UPS system 100.
FIG. 2 is a simplified schematic showing AC/DC converter 102 and DC/AC converter 104 in more detail. AC/DC converter 102 may illustratively be a rectifier and illustratively include three complementary pairs of switched semiconductor devices 200, one pair for each phase, that provide rectification. Respective junctions 2081-3 of the complementary pairs provide power inputs for each of the three phases, thus providing AC/DC converter 102 with a three phase power input 209. Each of rectifier fuses F1-3 is coupled to a respective one of the junctions 2081-3. Switched semiconductor devices 200 may be silicon controlled rectifiers, MOSFETs, thyristors, IGBTs, or other switched semiconductor devices that provide rectification. Gates 202 (only two of which are identified by reference number 202 in FIG. 2) of switched semiconductor devices 200 are coupled to outputs 136 of control module 132.
DC/AC converter 104 may illustratively be an inverter and where UPS system 100 has a three phase output, include three complementary pairs of switched semiconductor devices 204, one pair for each phase. Switched semiconductor devices 204 may illustrative be IGBTs, MOSFETS, SCRs, thyristors, or other switched semiconductor devices. Gates 206 (only two of which are identified by reference number 206 in FIG. 2) of switched semiconductor devices 204 are coupled to outputs 136 of control module 132.
It should be understood that the power supply system can be other than a UPS system. For example, the power supply system can be a power conditioning system 900 having AC/DC converter 102, DC/AC converter 104, but without back-up DC power source 106 as shown in FIG. 9. Alternatively, power supply system 1000 may have the DC bus 118 coupled to a DC/DC converter 1002 as shown in FIG. 10. In an aspect, power supply system 1000 can be an uninterruptible power supply system, in which case it would have a back-up DC power source, such as back-up DC power source 106 (shown in phantom in FIG. 10), coupled to DC bus 118. Alternatively, power supply system 1100 may have DC bus 118 coupled directly to output 1102 of power supply system 1100, so that DC bus 118 is coupled directly to a DC load 1104, as shown in FIG. 11.